Several methods and systems for setting up and using alternative communication paths between endpoints in layer-2 networks are known in the art. Alternative communication paths can be used in order to provide protection against failures and/or traffic load balancing. For example, link aggregation (LAG) is a technique by which a group of parallel physical links between two endpoints can be joined together into a single logical link. For Ethernet™ networks, link aggregation is defined by Clause 43 of IEEE Standard 802.3, Carrier Sense Multiple Access with Collision Detection (CSMA/CD) Access Method and Physical Layer Specifications (2002 Edition), which is incorporated herein by reference.
Another scheme that uses alternative links or ports is described in “Ethernet Protection Switching,” Recommendation G.8031/Y.1342 of the International Telecommunication Union Telecommunication Standardization Sector (ITU-T), June, 2006, which is incorporated herein by reference.
The IEEE 802.1 standards specify several methods for establishing alternative paths using spanning-tree protocols (STP). Rapid STP (RSTP) is a version of STP that enables fast convergence of the communication path following network topology changes. RSTP is described in the IEEE 802.1D standard, 2004 edition, entitled “IEEE Standard for Local and Metropolitan Area Networks—Media Access Control (MAC) Bridges,” which is incorporated herein by reference.
The IEEE 802.1Q standard, 2003 edition, entitled “IEEE Standards for Local and Metropolitan Area Networks—Virtual Bridged Local Area Networks,” which is incorporated herein by reference, describes a multiple spanning tree protocol (MSTP), for use in networks that contain multiple virtual local area networks (VLANs).
Another form of providing alternative paths in a layer-2 network is by using bidirectional ring networks. For example, some networks comprise Resilient Packet Ring (RPR) configurations, as defined by the IEEE 802.17 working group. Applicable standards and additional details regarding RPR network configurations are available at www.ieee802.org/17.
Several methods and systems are known in the art for fast switch-over between alternative communication paths over ring networks. For example, Extreme Networks, Inc. (Santa Clara, Calif.) offers a protection solution called Ethernet Automatic Protection switching (EAPS). Further details regarding this product are available at www.extremenetworks.com. Foundry Networks, Inc. (Santa Clara, Calif.) uses a protocol called Metro Ring Protocol (MRP). Further details regarding this product are available at www.foundrynet.com. Telco Systems (Kfar Netter, Israel), a BATM company, offers a protocol called Fast Ring Solution (T-FRS). Further details regarding T-FRS are available at www.batm.com/files/docs/metroethernetring.pdf.